Traditional telephone system:
PSTN public switch telephone network
Central office:
NADP: North America Dialing Plan – routing protocol
Demarc box: outside demark box charged by telephonecompany; inside demark box is chargedby yourself.
Trunk Lines: every single line has its ownphone number. One trunk line only allowone call in or one call out.
Hunt group: incoming calls -- have mainnumber. If one trunk line is busy then forward to the other trunk line in thegroup. Handled by central office.
outgoing calls: – controlled by PBX -- can program thetelephone system outgoing call on your PBX.
The phone system:
PBX: the server that route all the calls.
Voicemail: usually separate with PBXserver. Run all the voice stuff.
AA: Auto Attendance. The option is programed in PBX, but the voiceis located on Voice mail box sitting on the voice system.
Stations:
Digital/analog, digital PBX + digital station. Analog PBX – Analog station. Digital PBX have a couple of analog ports.
Subscribers:
Voice mail – don’t have to have a physicaltelephone, can route directly to theirmailbox.
Ports: the ports you buy determine how manypeople you can voice mail them in one time.
VoIP telephone system:
VoIP servers: (IP IPBX) – can rent or purchase.
Createextension with userID&passwd
IP trunk line: over Ethernet. VS normal trunk line.
VoIP client: can use the userID&passwd to register onthe VoIP server.
hard phone ---computers looks like phones , can accessvia web browser.
soft phone
VoIP gateways:
Send IP phone signal to normal phoneline.
Connect different communicationinfrastructure. Allow skype switch toSIP or normal phone line.
VoIP protocols:
SIP: session initiated protocol. Cisco/Polycom sip phone.
Privateprotocol
VoIP codecs
4.5kbps.at least per user.
Network latency and QoS
Latency:75ms. <100ms.
Traditionlatecy: 45ms.
Unified communication: combine into youroutlook, switch to voice and txtfile.
Voip server, remote location site’s ip phones canregister to this ip-pbx server remotely!
原文：http://41080138.blog.51cto.com/2587513/1902828